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1.
Sci Rep ; 14(1): 20163, 2024 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-39215030

RESUMO

The field of data exploration relies heavily on clustering techniques to organize vast datasets into meaningful subgroups, offering valuable insights across various domains. Traditional clustering algorithms face limitations in terms of performance, often getting stuck in local minima and struggling with complex datasets of varying shapes and densities. They also require prior knowledge of the number of clusters, which can be a drawback in real-world scenarios. In response to these challenges, we propose the "hybrid raven roosting intelligence framework" (HRIF) algorithm. HRIF draws inspiration from the dynamic behaviors of roosting ravens and computational intelligence. What distinguishes HRIF is its effective capacity to adeptly navigate the clustering landscape, evading local optima and converging toward optimal solutions. An essential enhancement in HRIF is the incorporation of the Gaussian mutation operator, which adds stochasticity to improve exploration and mitigate the risk of local minima. This research presents the development and evaluation of HRIF, showcasing its unique fusion of nature-inspired optimization techniques and computational intelligence. Extensive experiments with diverse benchmark datasets demonstrate HRIF's competitive performance, particularly its capability to handle complex data and avoid local minima, resulting in accurate clustering outcomes. HRIF's adaptability to challenging datasets and its potential to enhance clustering efficiency and solution quality position it as a promising solution in the world of data exploration.

2.
Sci Rep ; 14(1): 18039, 2024 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-39098877

RESUMO

Coronavirus has long been considered a global epidemic. It caused the deaths of nearly 7.01 million individuals and caused an economic downturn. The number of verified coronavirus cases is increasing daily, putting the whole human race at danger and putting strain on medical experts to eradicate the disease as rapidly as possible. As a consequence, it is vital to predict the upcoming coronavirus positive patients in order to plan actions in the future. Furthermore, it has been discovered all across the globe that asymptomatic coronavirus patients play a significant part in the disease's transmission. This prompted us to incorporate similar examples in order to accurately forecast trends. A typical strategy for analysing the rate of pandemic infection is to use time-series forecasting technique. This would assist us in developing better decision support systems. To anticipate COVID-19 active cases for a few countries, we recommended a hybrid model utilizing a fuzzy time series (FTS) model mixed with a non-linear growth model. The coronavirus positive case outbreak has been evaluated for Italy, Brazil, India, Germany, Pakistan, and Myanmar through June 5, 2020 in phase-1, and January 15, 2022 in phase-2, and forecasts active cases for the next 26 and 14 days respectively. The proposed framework fitting effect outperforms individual logistic growth and the fuzzy time series techniques, with R-scores of 0.9992 in phase-1 and 0.9784 in phase-2. The proposed model provided in this article may be utilised to comprehend a country's epidemic pattern and assist the government in developing better effective interventions.


Assuntos
COVID-19 , Previsões , SARS-CoV-2 , Humanos , COVID-19/epidemiologia , Previsões/métodos , SARS-CoV-2/isolamento & purificação , Lógica Fuzzy , Modelos Logísticos , Pandemias
3.
New Gener Comput ; 40(4): 1125-1141, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35730008

RESUMO

One of the most difficult research areas in today's healthcare industry to combat the coronavirus pandemic is accurate COVID-19 detection. Because of its low infection miss rate and high sensitivity, chest computed tomography (CT) imaging has been recommended as a viable technique for COVID-19 diagnosis in a number of recent clinical investigations. This article presents an Internet of Medical Things (IoMT)-based platform for improving and speeding up COVID-19 identification. Clinical devices are connected to network resources in the suggested IoMT platform using cloud computing. The method enables patients and healthcare experts to work together in real time to diagnose and treat COVID-19, potentially saving time and effort for both patients and physicians. In this paper, we introduce a technique for classifying chest CT scan images into COVID, pneumonia, and normal classes that use a Sugeno fuzzy integral ensemble across three transfer learning models, namely SqueezeNet, DenseNet-201, and MobileNetV2. The suggested fuzzy ensemble techniques outperform each individual transfer learning methodology as well as trainable ensemble strategies in terms of accuracy. The suggested MobileNetV2 fused with Sugeno fuzzy integral ensemble model has a 99.15% accuracy rate. In the present research, this framework was utilized to identify COVID-19, but it may also be implemented and used for medical imaging analyses of other disorders.

4.
J Neuroradiol ; 37(5): 277-83, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20381865

RESUMO

PURPOSE: Meningiomas are the most common extraaxial intracranial type of tumor, and their management and prognosis depend on their grade and histology. Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) are two new imaging techniques that have proved helpful in elucidating the microarchitecture of brain tumors. The aim of the present study was to assess the role of diffusion and diffusion tensor metrics in the identification and classification of meningioma grades and subtypes. METHODS AND MATERIALS: A total of 21 consecutive patients with meningioma were included in this retrospective study, of whom 16 had benign meningiomas (three fibroblastic, 11 transitional/mixed, two meningothelial) and five had atypical meningiomas. Tumor mean diffusivity (Dav), fractional anisotropy (FA), linear anisotropy (CL), planar anisotropy (CP), spherical anisotropy (CS) and eigenvalues (e1, e2, e3) were measured in all cases, and differences in diffusion tensor metrics between atypical, fibroblastic and other benign (transitional, meningothelial) meningiomas were statistically analyzed using the Mann-Whitney test. RESULTS: No statistically significant differences were found among the mean Dav values for atypical, fibroblastic and other benign meningiomas. Both atypical and fibroblastic meningiomas showed significantly higher mean FA values and lower mean CS values compared with other meningiomas (P<0.01), but no statistically significant difference in these values between each other. Atypical meningiomas showed higher CL values compared with fibroblastic and other benign meningiomas but, again, the difference was not statistically significant. Both atypical and fibroblastic meningiomas showed statistically significantly higher CP values and lower e3 values compared with transitional meningiomas (P<0.01). CONCLUSION: These results suggest that diffusion tensor metrics may be helpful in the differentiation of atypical, fibroblastic and other benign meningiomas.


Assuntos
Imagem de Tensor de Difusão , Neoplasias Meníngeas/patologia , Meningioma/patologia , Adulto , Idoso , Anisotropia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Neoplasias Meníngeas/classificação , Meningioma/classificação , Pessoa de Meia-Idade , Estudos Retrospectivos , Estatísticas não Paramétricas
5.
J Laryngol Otol ; 134(3): 247-251, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32172693

RESUMO

OBJECTIVES: The primary goal of rhinoplasty is patient satisfaction and improved quality of life. The present study was conducted to assess patient satisfaction with face and nose appearance, and quality of life after rhinoplasty. METHODS: Patients presenting for rhinoplasty completed the FACE-Q survey. This is a new instrument that measures patient-reported outcomes in those undergoing aesthetic procedures. The FACE-Q scales include satisfaction with facial appearance overall, satisfaction with the nose, psychological well-being, psychosocial distress and social function. RESULTS: Sixty-five patients completed the FACE-Q at pre-operative and at post-operative follow-up visits. Post-operative scores increased significantly in terms of: satisfaction with facial appearance (p < 0.0001, t = 15.639, degrees of freedom = 64); social function (p < 0.0001, t = 12.208, degrees of freedom = 64); psychosocial distress (p < 0.0001, t = 13.864, degrees of freedom = 64); psychological function (p < 0.0001, t = 12.681, degrees of freedom = 64); and satisfaction with nose (p < 0.0001, t = 16.421, degrees of freedom = 64). Most patients reported more than 79 per cent satisfaction with the post-operative outcome. CONCLUSION: The FACE-Q is an adequate instrument for determining successful aesthetic surgery based on patient satisfaction.


Assuntos
Satisfação do Paciente , Complicações Pós-Operatórias/psicologia , Qualidade de Vida , Rinoplastia/psicologia , Estresse Psicológico/psicologia , Adolescente , Adulto , Imagem Corporal/psicologia , Face/cirurgia , Feminino , Humanos , Índia , Masculino , Nariz/cirurgia , Medidas de Resultados Relatados pelo Paciente , Complicações Pós-Operatórias/diagnóstico , Período Pós-Operatório , Estudos Prospectivos , Escalas de Graduação Psiquiátrica , Comportamento Social , Estresse Psicológico/diagnóstico , Resultado do Tratamento , Adulto Jovem
6.
Int J Pediatr Otorhinolaryngol ; 137: 110173, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32658798

RESUMO

OBJECTIVE: To assess whether cochlear nerve (CN) cross-sectional area as measured with parasagittal magnetic resonance imaging (MRI) in prelingual pediatric deaf patients correlates with auditory performance after cochlear implantation. STUDY DESIGN: Prospective Cohort study. METHODS: Thirty-two prelingual children with bilateral profound sensorineural hearing loss (SNHL) who received unilateral cochlear implant were included in this study. Diameters of CN at Internal auditory canal (IAC) fundus and mid-point of IAC were retrospectively measured on parasagittal images of FIESTA (Fast Imaging Employing Steady-state Acquisition) sequence MRI by two independent observers. Cross-sectional areas [π (Height/2) (Width/2)] were then correlated with post-operative CAPS (Categories of Auditory Performance) and IT-MAIS (Infant-Toddler Meaningful Auditory Integration Scale) scores regularly assessed at 3 monthly intervals post device activation. RESULTS: The cochlear nerve was identified in all the 32 patients. Mean cross-sectional areas (CSA) of cochlear nerve were 0.71 ± 0.16 mm2 at IAC fundus and 0.73 ± 0.18 mm2 at mid-point of IAC. The correlation value between CSA at mid-point of IAC and CAPS score at 6 months was 0.271 (p-value- 0.140) and correlation value between CSA at mid-point of IAC and IT-MAIS score at 6 months was 0.282 (p-value- 0.124) which were statistically not significant. CONCLUSION: There was no significant correlation between the cross-sectional areas of the cochlear nerve on MRI and postoperative auditory scores as measured by CAPS and IT-MAIS scores at six months from the device activation. Hence, we conclude that above an adequate diameter, which can affect the minimum required neurons, the changes in the diameter do not have significant bearing on auditory outcomes after cochlear implantation.


Assuntos
Nervo Coclear/diagnóstico por imagem , Perda Auditiva Bilateral/cirurgia , Perda Auditiva Neurossensorial/cirurgia , Audição , Criança , Pré-Escolar , Implante Coclear , Implantes Cocleares , Nervo Coclear/patologia , Orelha Interna , Feminino , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Osso Petroso , Período Pós-Operatório , Estudos Prospectivos , Estudos Retrospectivos
7.
Br J Neurosurg ; 23(1): 79-82, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19234914

RESUMO

We describe a rare case of an unusually located gangliocytoma. The conventional magnetic resonance imaging (MRI) appearance was suggestive of an olfactory groove meningioma. However, advanced MRI sequences (diffusion-weighted imaging--DWI; perfusion MRI; susceptibility-weighted imaging--SWI; MR spectroscopy--MRS) revealed features more consistent with a glial neoplasm.


Assuntos
Neoplasias Encefálicas/patologia , Lobo Frontal/patologia , Ganglioneuroma/patologia , Neoplasias Meníngeas/patologia , Meningioma/patologia , Diagnóstico Diferencial , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Adulto Jovem
8.
Interv Neuroradiol ; 25(4): 469-473, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30922201

RESUMO

BACKGROUND: Metameric spinal cord arteriovenous malformations (AVMs) are rare lesions characterized by an intradural and extradural component. They are difficult to treat surgically by the endovascular route. We report a case in which symptomatic relief was achieved by embolization of the extradural component only. CASE PRESENTATION: A 35-year-old woman presented with acute worsening of back pain, weakness in the left leg and urinary retention. Spinal angiography showed a metameric spinal cord AVM with partial common venous drainage of the extradural and intradural components. CONCLUSIONS: Targeted embolization of the extradural component led to dramatic improvement of the patient's symptoms, probably by achieving venous decongestion. She remains neurologically stable at two years' follow-up.


Assuntos
Malformações Arteriovenosas/terapia , Embolização Terapêutica , Medula Espinal/irrigação sanguínea , Adulto , Feminino , Humanos , Indução de Remissão , Fatores de Tempo
9.
J Pharm Anal ; 7(2): 134-140, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29404029

RESUMO

A stability-indicating reverse phase-high performance liquid chromatography (RP-HPLC) method was developed and validated for the determination of atazanavir sulfate in tablet dosage forms using C18 column Phenomenix (250 mm×4.6 mm, 5 µm) with a mobile phase consisting of 900 mL of HPLC grade methanol and 100 mL of water of HPLC grade. The pH was adjusted to 3.55 with acetic acid. The mobile phase was sonicated for 10 min and filtered through a 0.45 µm membrane filter at a flow rate of 0.5 mL/min. The detection was carried out at 249 nm and retention time of atazanavir sulfate was found to be 8.323 min. Linearity was observed from 10 to 90 µg/mL (coefficient of determination R2 was 0.999) with equation, y=23.427x+37.732. Atazanavir sulfate was subjected to stress conditions including acidic, alkaline, oxidation, photolysis and thermal degradation, and the results showed that it was more sensitive towards acidic degradation. The method was validated as per ICH guidelines.

10.
Am J Surg ; 147(3): 387-9, 1984 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-6703213

RESUMO

Nine hundred fifty cases of moderate to large hydrocele were surgically treated by excising the skin, dartos, spermatic fascia, sac, and the median septum, leaving sufficient scrotal skin to construct a new scrotum--just enough to accommodate both the testes. The cure was complete, and the postoperative complications were minimal. The redundant skin and subcutaneous tissues were removed because they would otherwise hang and flop against the inner aspect of the patient's thighs, resulting in great difficulty and dissatisfaction in walking. This method of skin excision can also be applied to a huge inguinoscrotal hernia after its repair.


Assuntos
Hidrocele Testicular/cirurgia , Adulto , Idoso , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias
11.
Am J Surg ; 149(5): 686-90, 1985 May.
Artigo em Inglês | MEDLINE | ID: mdl-3993854

RESUMO

Three hundred fifty patients with elephantiasis of the penis and scrotum were surgically treated by excision of all elephantoid skin and subcutaneous tissues. Before attempting to excise the extensive elephantoid tissues, the spermatic cord and testes with their coverings were taken out by two small lateral incisions, which made the operation easier and less time-consuming and minimized the complications. The skin of the scrotal neck was found to be the best for reconstruction of the scrotum to accommodate the two testes. The fascial penis is an ideal bed for intermediate split-thickness skin grafts. There was mechanical improvement in the physical disability, restoration of potency and sexual habits, and reduction of mental anguish.


Assuntos
Elefantíase/cirurgia , Linfedema/cirurgia , Doenças do Pênis/cirurgia , Escroto , Adulto , Idoso , Doenças dos Genitais Masculinos/cirurgia , Humanos , Masculino , Métodos , Pessoa de Meia-Idade , Pênis/cirurgia , Escroto/cirurgia
12.
J Pharm Sci ; 83(12): 1651-6, 1994 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-7891290

RESUMO

The secondary structure content of microparticulate insulin powders produced by the supercritical antisolvent (SAS) precipitation technique was investigated via Raman spectroscopy. Precipitate samples were generated at 25 and 35 degrees C processing temperatures. Both precipitate samples gave amide I band spectra that were shifted roughly +10 cm-1 relative to the commercial powder. The corresponding secondary structure estimates had significantly increased beta-sheet contents with concomitant decreases in alpha-helix contents relative to the commercial protein; the sum of beta-turn and random coil content remained essentially unchanged. The magnitude of the perturbation was slightly greater for the 35 degrees C sample. Dissolution of the commercial powder and precipitates in 0.01 M HCl yielded solution structure estimates similar to that of the commercial powder. An analysis of insulin in dimethyl sulfoxide, the suspending solvent in the SAS process, indicated that some, but not all, of the structural change observed for the precipitate samples may be attributed to solvent exposure. These results are suggestive of extensive beta-sheet-mediated intermolecular interactions in precipitate states, consistent with analyses of irreversible protein aggregate/fibril states. Interestingly, unlike irreversible protein aggregates, the insulin powders recover essentially full biological activity on reconstitution.


Assuntos
Insulina/química , Estrutura Secundária de Proteína , Fenômenos Químicos , Precipitação Química , Química Farmacêutica/métodos , Físico-Química , Dimetil Sulfóxido , Estudos de Viabilidade , Ácido Clorídrico , Tamanho da Partícula , Pós , Soluções , Análise Espectral Raman
13.
Indian J Dermatol ; 58(5): 406, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24082199

RESUMO

Botryomycosis is a rare chronic bacterial granulomatous disease that usually involves skin and rarely viscera. Main etiological agent is Staphylococcus aureus and less commonly Pseudomonas spp., Escherichia coli, Proteus spp., Streptococcus spp. We here report a case of 32-year-old male with polymicrobial botryomycosis on forehead and on frontal scalp. Culture from lesions revealed growth of S. aureus initially. Partial resolution was achieved with cefadroxyl and clavulanic acid, rifampicin, and linezolid. Subsequent repeat culture revealed E. coli sensitive to netilmycin. Slow and steady resolution was achieved with surgical debridement and combination therapy of injectable netilmycin and oral sufomethoxazole and trimethoprim for a prolonged period.

15.
Neuroradiol J ; 24(6): 862-6, 2011 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-24059887

RESUMO

We describe a 43-year-old man with a long-standing history of headache and ophthalmoplegia. Brain MRI showed a nodular enhancing lesion at the root exit zone of the left oculomotor nerve. Contrast enhancement on follow-up MRI and clinical symptoms showed a partial resolution on starting prophylactic anti-migraine medications. This was confirmed to be a case of ophthalmoplegic migraine. Here we describe a rare case of OM in an adult patient with its characteristic imaging pattern and the differential diagnosis considered.

16.
Singapore Med J ; 50(4): e133-7, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19421667

RESUMO

Cryptococcal infection of the brain is commonly seen in immunocompromised patients but rarely considered as the differential diagnosis in immunocompetent patients. We present two cases of cryptococcosis involving the brain in immunocompetent patients, which strongly mimicked tuberculous infection in both conventional as well as advanced magnetic resonance (MR) imaging, and the disease was only confirmed after histopathological/cerebrospinal fluid serological study. One patient was a 52-year-old woman, and the second patient was a 23-year-old man. These two cases highlight the need for workup of fungal infections in immunocompetent patients from the tuberculous endemic regions, even when the imaging is highly suspicious of tuberculous lesions. The imaging findings in advanced MR imaging techniques such as diffusion, perfusion, susceptibility-weighted imaging and MR spectroscopy are discussed.


Assuntos
Cryptococcus neoformans , Imagem de Difusão por Ressonância Magnética , Imunocompetência , Imageamento por Ressonância Magnética , Meningite Criptocócica/diagnóstico , Tomografia Computadorizada por Raios X , Tuberculose Meníngea/diagnóstico , Anfotericina B/administração & dosagem , Antifúngicos/administração & dosagem , Doenças Cerebelares/diagnóstico , Doenças Cerebelares/patologia , Doenças Cerebelares/cirurgia , Diagnóstico Diferencial , Feminino , Flucitosina/administração & dosagem , Humanos , Espectroscopia de Ressonância Magnética , Masculino , Meninges/patologia , Meningite Criptocócica/imunologia , Meningite Criptocócica/patologia , Meningite Criptocócica/cirurgia , Pessoa de Meia-Idade , Tuberculose Meníngea/imunologia , Tuberculose Meníngea/patologia , Tuberculose Meníngea/cirurgia , Adulto Jovem
17.
Neuroradiol J ; 21(2): 192-5, 2008 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-24256825

RESUMO

We report an unusual case of a 54-year-old man with third nerve palsy caused by an extra-axial cavernoma in relation to the cisternal portion of the oculomotor nerve. In addition to this lesion, the patient had multiple intracranial cavernomas. Interestingly, an initial MRI without T2* gradient sequence missed the multiple cavernomas. A subsequent MRI done after one month showed an increase in size with fluid level within the extra-axial cavernoma.

18.
Biophys J ; 70(6): 2888-902, 1996 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-8744327

RESUMO

We simulated the structure of reversible protein aggregates as a function of protein surface characteristics, protein-protein interaction energies, and the entropic penalty accompanying the immobilization of protein in a solid phase. These simulations represent an extension of our previous work on kinetically irreversible protein aggregate structure and are based on an explicit accounting of the specific protein-protein interactions that occur within reversible aggregates and crystals. We considered protein monomers with a mixture of hydrophobic and hydrophilic surface regions suspended in a polar solvent; the energetic driving force for aggregation is provided by the burial of solvent-exposed hydrophobic surface area. We analyzed the physical properties of the generated aggregates, including density, protein-protein contact distributions, solvent accessible surface area, porosity, and order, and compared our results with the protein crystallization literature as well as with the kinetically irreversible case. The physical properties of reversible aggregates were consonant with those observed for the irreversible aggregates, although in general, reversible aggregates were more stable energetically and were more crystal-like in their order content than their irreversible counterparts. The reversible aggregates were less dense than the irreversible aggregates, indicating that the increased energetic stability is derived primarily from the optimality rather than the density of the packing in the solid phase. The extent of hydrophobic protein-protein contacts and solvent-exposed surface area within the aggregate phase depended on the aggregation pathway: reversible aggregates tended to have a greater proportion of hydrophobic-hydrophobic contacts and a smaller fraction of hydrophobic solvent-exposed surface area. Furthermore, the arrangement of hydrophobic patches on the protein surface played a major role in the distribution of protein contacts and solvent content. This was readily reflected in the order of the aggregates: the greater the contiguity of the hydrophobic patches on the monomer surface, the less ordered the aggregates became, despite the opportunities for rearrangement offered by a reversible pathway. These simulations have enhanced our understanding of the impact of protein structural motifs on aggregate properties and on the demarcation between aggregation and crystallization.


Assuntos
Proteínas/química , Fenômenos Biofísicos , Biofísica , Cristalização , Técnicas In Vitro , Substâncias Macromoleculares , Modelos Químicos , Estrutura Molecular , Método de Monte Carlo , Solventes , Propriedades de Superfície , Termodinâmica
19.
Biotechnol Bioeng ; 52(2): 193-203, 1996 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-18629888

RESUMO

We describe a new protein characterization technique called self-interaction chromatography (SIC), which exploits the specificity of protein-protein interactions that is common to protein aggregates and enables the rapid screening of protein formulation additives as physical stabilizers against aggregation. This technique also enables the identification of specific interaction sites and the determination of their relative importance for self-association. Mannitol, glycine, and dextran 40 were tested for their stabilizing effect toward the model protein lysozyme. Dextran 40 exhibited a poor stabilizing effect. While mannitol stabilized both the native and acid-denatured forms of lysozyme, glycine stabilized the native form with respect to the denatured species. These results are in good agreement with findings in the formulation literature. The SIC shows tremendous potential as a rapid formulation development tool. We also screened two putative interaction sites for involvement in the self-association of lysozyme and estimated the associated binding energies using a binding isotherm model that we developed. The sites screened consisted of residues 41-48 and 125-128 and were selected based on their apparent importance in forming crystal contacts in several different crystal forms of lysozyme. Of the two sites, only residues 125-128 were found to influence self-association under the conditions we employed. Because the success of this technique depends on the exploitation of self-interactions between native species, several important applications are also suggested such as separating native from misfolded or variant species and probing site utilization in aggregation versus crystallization phenomena.

20.
Biophys J ; 66(5): 1274-89, 1994 May.
Artigo em Inglês | MEDLINE | ID: mdl-8061184

RESUMO

We have simulated the structure of kinetically irreversible protein aggregates in two-dimensional space using a lattice-based Monte-Carlo routine. Our model specifically accounts for the intermolecular interactions between hydrophobic and hydrophilic protein surfaces and a polar solvent. The simulations provide information about the aggregate density, the types of inter-monomer contacts and solvent content within the aggregates, the type and extent of solvent exposed perimeter, and the short- and long-range order all as a function of (i) the extent of monomer hydrophobic surface area and its distribution on the model protein surface and (ii) the magnitude of the hydrophobic-hydrophobic contact energy. An increase in the extent of monomer hydrophobic surface area resulted in increased aggregate densities with concomitant decreased system free energies. These effects are accompanied by increases in the number of hydrophobic-hydrophobic contacts and decreases in the solvent-exposed hydrophobic surface area of the aggregates. Grouping monomer hydrophobic surfaces in a single contiguous stretch resulted in lower aggregate densities and lower short range order. More favorable hydrophobic-hydrophobic contact energies produced structures with higher densities but the number of unfavorable protein-protein contacts was also observed to increase; greater configurational entropy produced the opposite effect. Properties predicted by our model are in good qualitative agreement with available experimental observations.


Assuntos
Simulação por Computador , Modelos Químicos , Proteínas/química , Fenômenos Biofísicos , Biofísica , Substâncias Macromoleculares , Estrutura Molecular , Método de Monte Carlo , Conformação Proteica , Soluções , Solventes , Propriedades de Superfície , Termodinâmica
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